1. Field of Invention
The present invention relates to a method and apparatus of image processing to detect and enhance edges and to reduce noise in medical imaging, e.g. ultrasound imaging, X-ray, MRI, CT. Specifically, the method and apparatus of the present invention relates to the detection of edges in noisy images and enhancement of such edges.
2. Description of Related Art
An object, such as an organ, in an image has borders or edges and image processing can detect these borders or edges. Detection of edges is usually performed with filters 11 as shown in FIGS. 1a-1c. However, it is difficult to detect edges in an image with noise (or poor signal to noise ratio). Edges of noise patterns can be erroneously detected as “edges” rather than the true edges of an object or organ for example. Therefore, a low-pass filter is usually applied to the image before the edge detection in order to reduce noise and to detect the true edges reliably. A low-pass filter can be 3×3, 5×5 or 7×7 or more in size. Such filters are known in the art and examples are illustrated in FIGS. 2a-2c. After the low-pass filter is applied, edge detection is performed using, for example, the filter shown in FIG. 1a. The low-pass filter smoothes the image and reduces noise. However, low-pass filter masks override each other when the filter in FIG. 1a is used, resulting in somewhat fuzzy edges as well as spatial errors with respect to the true edges of the original image. What is therefore needed is a method to detect true edges in images containing noise which does not result in the production of fuzzy edges or spatial errors.